Detection and sub-cellular distribution of the amnesic shellfish toxin, domoic acid, in the digestive gland ofOctopus vulgarisduring periods of toxin absence

Domoic acid (DA) is a neurotoxin produced by Pseudo-nitzschia diatoms that is accumulated in the highest concentrations in filter-feeding organisms, such as bivalve molluscs. Although DA is a water-soluble molecule that is rapidly cleared from most marine organisms, it appears that octopus may consistently contain DA in the digestive gland. To test this hypothesis, specimens of Octopus vulgaris were caught for DA analysis when Pseudo-nitzschia cells were not observed in seawater and DA was not detected in octopus food items, i.e. mussels. DA was consistently detected in each octopus specimen (n=32) analysed and its concentrations varied from 1.0 to 26.6 µg g−1. DA sub-cellular distribution was evaluated in the digestive gland of six specimens in order to prove whether DA preferably accumulates in some cell compartment. DA was predominantly found (>90%) in the soluble fraction (cytosol) and to a lesser extent in the insoluble fractions (nucleic, mitochondrial, lysosomal, microsomal). This disposit...